The invention relates to a process for textile cleaning and disinfection by means of plasma representing a new way towards a waterless washing machine. Furthermore, the invention relates to a lock or room for inactivating viruses, bacteria and spores, and also for purifying air in the conventional sense such as from dust, pollen, odors or the like.
There are various dangers to health, e. g., caused by polluted air. In addition to gaseous components and aerosols of anthropogenic origin, in particular biological components such as viruses, spores, bacteria or pollen. Viruses and bacteria can be transmitted from contaminated areas through living beings, vehicles or parcels. Recently, virological dangers such as H5N1 (bird flu), influenza or SARS mainly became the focus since there's risk of pandermics. In the normal case, for infection a sufficiently high concentration of the infectious matter is required.
Apart from the indoor air or ambient air, often exhaust gases or waste air carry microorganism strains which are harmful for health and environment. In many cases, the exhaust gases or the waste air are repeatedly charged with aerosols. These can additionally be the carriers of disturbing odors or volatile organic compounds (VOCs). VOC is to be understood as harmful hydrocarbon compounds.
Aerosols is the generic term of solid and liquid particulates. In particular, smaller aerosols in the range of a few nanometers are especially harmful. These impurities often indicated as nanoparticulates are able to uncheckedly enter into the human lungs, or even to immediately be assimilated through the skin. The most known example of such nanoparticulates is the particulate matter in diesel exhaust gases. Further, in the indoor air often harmful substances such as particulates of cigarette smoke, toner of photocopiers or paper dust of copy paper are contained.
Various measures are taken in order to reduce concentrations of microorganism strains in the exhaust gases or waste air. Conventional means such as mechanical separators, mechanical filters, gas washers or combustion are only in a limited use, are too costly or consume too much energy.
Specially for the separation of aerosols, and in particular the removal of macroscopic dust particles from industrial exhaust gases electrostatic filters or even electrostatic precipitators for the purification are known. This process also being referred to as electrical gas scrubbing includes electric charging of dust particles with corona discharge as a standard step. A typical geometry consists of a thin wire which is enclosed by a cylinder spaced from the wire. According to polarity of the wire electrode a distinction is made between negative corona and positive corona. With the negative corona, the electron attachment results in the generation of negative ions attaching to aerosols as the case may be. Sometimes, this process is also described as the ion blow.
The electrostatic precipitators comprise so called collecting electrodes and discharge electrodes with appropriate high-voltage fields between them. The dust particles collected on the collecting electrode are mechanically removed which is disadvantageous in certain applications. Also, the high voltages of several 10 kilovolts required for the electrostatic precipitators are disadvantageous.
In DE 34 20 973 A1 there is proposed a combination including filter mats on which the removed dust can be collected.
In DE 102 45 902 A1 the collecting electrode includes a space into which the particles are able to enter and inside of which no potential difference is prevailing.
In DE 30 04 474 C2 the corona-starting voltage below flashover voltage is superimposed by a pulse voltage having pulse widths ranging from ns to ms.
According to DE 43 39 611 A1, charging of dust particles in the entire volume, a homogeneous collection surface and prevention of electric disruptive discharges shall be achieved in that a segmentation is taking place in the flow direction in which dielectric barrier discharge paths for charging dust particles alternate with “normal” collecting paths having high homogeneous electric fields between metallic electrodes. The dielectric barrier discharge is operated between a dielectric diode and the collecting electrode, thus over the entire cross-section of the gas space. As a result, in this configuration very high voltages (alternating voltages in this case) are required similar to corona discharge, with a greater exhaust passage to achieve a small flow resistance. The common problems continue to exist for the corona portion.
Generally, it is also known that the most different chemical reactions which mainly proceed through very reactive species, so called radicals, can be initiated with plasmas. This has been analyzed and used for various applications of treating exhaust gases or even for plasma-chemical reactors. Then, solutions have been proposed which make use of dielectric barrier discharge for generating appropriate plasmas. Dielectric barrier discharges (hereinafter also DBDs) are characterized in that at least one of the conductive electrodes is provided with a dielectric thus forming an insulated electrode, or in that a dielectric is disposed between the conductive electrodes. The configuration of such arrangements can be multiform. Depending on this configuration and the remaining parameters specific characteristics of the DBD are often achieved. Sometimes, specific designations are used according to such configurations or according to the purpose of application (e.g. ozonizer).
Generally, the DBD can be operated with sinusoidal or square-wave AC voltages ranging from a few Hz up to several hundreds of kHz. Various embodiments of the DBD are known as a discharge configuration. Frequently, with the large-area electrodes, a plurality of small discharge threads also called filaments having a thickness of up to a few of tenths of millimeters and being statistically distributed for the most part are provided. In the transition region toward the insulated electrodes these filaments form spreadings which frequently pass over to surface gliding discharges having a plurality of further thin discharge channels.
Such phenomena of surface gliding discharge are able to be dominant in specific arrangements, so called coplanar discharge arrangements or surface discharge arrangements. It is also known that, in particular in gas fillings with inert gases and in thereof mixtures, respectively, discharge structures can be formed which are not filamented. Besides, various combinations and transient modifications of discharge embodiments are possible.
With reactors assembled according to the prior art in particular, aerosols cannot really be retained and decomposed within the plasma.
According to DE 197 17 890 C1, it is provided for an effective treatment of soot particles to collect particulate matter on a porous filter element and to expose it to the plasma of a DBD. A similar principle is indicated in DE 100 57 862 C1. With this principle, however, the problem of ash deposition and blockage continues to exist.
It is known from WO 2005/028081 and DE 103 44 489 A1, respectively, that a contiguous electrode being structured toward all directions in space is used, wherein insulating material is placed on the elevations thereof. This insulating material forms a delimiting face for the structured electrode. On the other side of the insulating material an additional electrode is mounted. The structured electrode consists of a wire mesh, contiguous or adjacent solids and structures, respectively, made of an electrically conductive material. At the same time, the structured electrode simultaneously functions as a spacer for additional plane surfaces and as a filter element. The discharge representing a specific configuration of a DBD develops in the clearances of the electrode structure and on the surface of the insulating material.
For some applications, the structure provides an excessive back pressure. In addition, the reactions within the plasma are often highly complex since all species generated within the plasma are able to be involved in the reactions.
An arrangement according to DE 198 26 831 A1 is further known wherein the plasma reactor consists of a tubular electrode which is coated with a dielectric barrier on its inner surface. A conductive electrode facing the gas space and made of a wire mesh, for example, is mounted as a counter electrode being in contact with the barrier. With appropriate voltages, it then results in the development of gas discharges within the gap area of the wire screen electrode and the dielectric barrier. Mixing the influent gas and the plasma region is carried out by means of vortex effects in the immediate area of the wire screen electrode.
In DE 196 16 206 A1 gas discharge is mainly generated on the surface of a dielectric wherein the electrode facing toward the gas provides an immediate contact with the dielectric and consists of thin bar stock having a rounded cross-section. Catalytically acting materials are located in a distance of some millimeters toward this electrode facing the gas, and are at the same potential.
With these arrangements, the restricted exchange between the plasma and remaining gas has an adverse effect on many applications and as a result on the plasma-induced reactions within the gas as well. Further, aerosols or soot particles cannot be separated since any filtering or separation is not available. Subsequently, in the plasma of such arrangements the aerosols/soot particles will not successfully be decomposed with it as well.
Applicants have provided an arrangement and method wherein plasma is generated with a dielectric barrier discharge arrangement within a large area region wherein an open structure of the DBD toward the face of the gas space for the influent gas is available. According to the method, ions are extracted from the plasma of DBD and accelerated in an electric field such that an ion blow covering the space for the influent exhaust gas and the waste air, respectively, is generated. In a simple embodiment, the electric field is developed for ion extraction by means of negative pulse voltages of the plasma generating portion of a dielectric barrier discharge. The face of the device opposing this DBD arrangement is at ground potential. Negative ions are accelerated toward the ground potential such that aerosols contained in the gas can be charged and separated. In another embodiment then, in addition to the separation of aerosols, the decomposition thereof within the plasma is also provided. For that, opposite dielectric barrier discharge arrangements are formed. The faces of the DBD arrangements opposing each other toward the gas space for the influent gas are then applied with positive and negative pulse voltages, respectively. In this way, charge carriers as well as charged aerosols drift, depending on the sign of the charge thereof, towards the electrode of the DBD each conducting opposite potential. There, the aerosols are separated and decomposed in the plasma of the respective DBD.
Such systems, in al., generate ozone such that a longer presence of living beings in such rooms or spaces is not possible.
Previous disinfection systems and air purification systems have different operation limits. Systems based on plasmas operate according to the air recirculation principle or the injection principle. Then, the room air including its harmful constituents is essentially treated by reactive species within the reactor portion. In another case, reactive constituents from a plasma unit are added into the room (such as with the disinfection by means of ozone). Such systems are only applicable to some extent, and only gaseous or gasborne constituents can be treated this way. It is also critical to observe treatment times (and so retention time) regarding the disinfection.
A very effective method of disinfection/air purification is provided with UV methods. At the same time, however, direct disinfection is only possible only without exposure of people. Also, recirculation mode and indirect disinfection are possible, but including similar problems as before.
With the routine disinfection including disinfectants, considerable losses of effectiveness at a falling temperature occur such that the pass-through vessels or epidemic or disease mats will be restricted in their effectiveness. Further, these means are not allowed to be directed to unprotected persons.
Cleaning and disinfection of textiles are connected with the employment of water and various cleaning agents and disinfectants as well. This requires a considerable consumption of our water resources resulting in varied water pollutions. Then, expensive sewage treatment processes are necessary.
The object and pollution level as well as the nature of pollution are very different. So, the whole panoply of applications is ranging from simple clothing up to cleanroom drapery, medical textiles or even protection equipment. The nature of pollution shows a still wider range. This extends from simple odor load of clothes beyond the pollution with bio-aerosols (microbes, spores, pollen) up to various other pollutions.
Treatment of textile fabric by means of plasma is known from the patent publications DE 19634725 A1 and DE 3248590 A1. Herein, the surfaces of textiles are treated in such a manner that with later necessary cleaning less power and water are needed. Complete cleaning by means of plasma is not carried out.
In JP 2005224757 A is disclosed a possibility of the surface cleaning of textiles by means of plasma. The plasma cleaning device is to save chemicals and cleansing agents, and comprises an iron having a water tank and plasma electrodes for plasma generating at a standard pressure. The water vapor is guided through the plasma wherein hydroxyl radicals are developed which clean the textiles.
Furthermore, there are devices by means of which the polluted air is disinfected through a UV unit and an ionisation unit. Known devices are described in DE 102005003923 A1 and in DE 102005035951 A1. Basically, with the employment of ultraviolet radiation and use of ozone connected therewith the following reaction mechanisms are known. Molecular oxygen (O2) is decomposed into oxygen radicals. The so developed oxygen radicals react themselves again with molecular oxygen during the formation of ozone. Under the influence of ultraviolet light the ozone being so developed can be decomposed into oxygen radical and molecular oxygen again. The oxygen radical is now available in order to react with water to two hydroxyl radicals or with molecular oxygen to ozone again.
Application for cleaning textiles is not provided herein.